The objectives of the MBRS program at York College - "Research and Training for Biomedical Career Development" - are to improve and strengthen the research environment and to broaden the scope of biomedical research in the department of Natural Sciences for two purposes: (1) to improve the research skills and increase the scholarly productivity of the faculty in the department, and (2) to provide the minority students with increased opportunities to acquire the knowledge, expertise and motivation that will (a) direct them towards careers in biomedical research and (b) enable them to compete successfully for positions in graduate and professional schools. To these ends support is requested for 6 projects in cell biology, physical chemistry, molecular biology, microbial and molecular genetics and organic chemistry. Support is also requested for 18 students who will participate in all phases of the planning and implementation of the research, as well as in the reporting and publication of the results. In project #1, "In Vitro Model for Prediction of Human Toxicity" an in vitro cell culture technique will be developed with potential to predict acute human toxicity to chemicals and drugs. In project #2, "Electronic Spectroscopy of Simple Porphyrins and Bacteriorhodopsin", excited electronic states of model biological chromophores will be studied. In project #3, "Sequence and Structure Signals for 5SRNA processing in Drosophila melanogaster", mutant RNAs will be produced and analyzed. In project #4, "Molecular Basis of Spontaneous Chromosome Rearrangements in the hemB gene of E. coli", the nucleotide sequences which promote insertions, deletions and other aberrations will be determined and analyzed. Project #5, "Ring Expanded Nucleoside Analogs and Related Compounds", will investigate stereochemical requirements for antiviral activity by the controlled synthesis of new types of nucleoside analogs and in project #6 "Uniquely labelled Amino Acids for Protein NMR", 2H, 13C, and 15N labelled amino acids will be synthesized and incorporated into proteins for further study by solution and solid state NMR. Subproject #3 is new to this MBRS proposal. All other subprojects are components of the MBRS grant currently held by York College.